Ladies and gentlemen, our nation is in a crisis. It is in a crisis about whether to label the current moment a crisis.

Facing the blanket refusal by the Trump administration to cooperate with any and all congressional oversight, House Judiciary Committee Chairman Jerrold Nadler (D-N.Y.) last week proclaimed a full-blown “constitutional crisis.” House Speaker Nancy Pelosi (D-Calif.) said she agreed.

On the other side, the man who precipitated the purported crisis, President Trump, respectfully disagreed. “The Democrats new and pathetically untrue sound bite is that we are in a ‘Constitutional Crisis,’ ” he remarked as part of a 118-tweet fusillade that included an attack on his handpicked FBI chief. “They are a sad JOKE! We may have the strongest Economy in our history.”

He wrote this before the Dow Jones industrial average tumbled more than 600 points because of his trade war with China.

Is it a crisis or not? And “Would we even know one if it bonked us on the heads?” asked Slate’s Dahlia Lithwick. She put the question to 10 legal experts and got a split decision: Four said no crisis, three said crisis, and three disputed the validity of the question. (They are lawyers, after all.) “Crisis schmisis,” replied Harvard’s Laurence Tribe.

If we’re not in a crisis yet, we certainly would be in one if (or when) the Trump administration ignores a court order, or if the Supreme Court (with Trump’s appointees) upholds a blatantly illegal act.

But Congress needn’t wait for the crisis to happen. Lawmakers can show the Trump administration how reckless its actions are by responding in kind, with their own brazen attempt to push their powers to the limit. For the first time in nearly 100 years, they should lock him up.

No, not Trump, and not his enabling attorney general, William Barr. That would be way too messy.

But there is another figure who is at once so disagreeable that even Republicans might not object to his confinement, and so ineffective that most people wouldn’t notice he’s missing: Treasury Secretary Steven Mnuchin.

Mnuchin has arguably been the most brazen in rejecting the constitutional balance. He’s refusing to turn over Trump’s tax returns even though the law explicitly states that the treasury secretary “shall furnish” any tax returns the chairman of the House Ways and Means Committee requests.

Some Democrats suggest they could punish such contempt of Congress witha $25,000-a-day fine. But that won’t work: Mnuchin literally prints the money. (Remember the photo of him and his wife at the mint looking like James Bond villains?) And his $300 million net worth would withstand 33 years of $25,000-a-day fines.

Much more likely to get Mnuchin’s attention would be for the House sergeant at arms to do what hasn’t been done since Teapot Dome days: seize him on his next Capitol drop-by, cuff him and put him in a chain-link cage — or what Trump officials who deal with child migrants call a Detention Space for Safety and Protection.

Contrary to Pelosi’s joke to The Post’s Robert Costa about “a little jail down in the basement of the Capitol,” no such holding cell remains for those in contempt of Congress. Therefore, Mnuchin’s cage should go in Statuary Hall, where tourists would snap photos. Rep. Maxine Waters (D-Calif.), chair of the House Financial Services Committee, would serve as his warden, and she would only release him for exercise breaks if he politely asks her to “bang the gravel.”

To persuade him to cooperate with Congress, Mnuchin would be fed only Buffalo chicken sandwiches from the takeout in the Capitol basement. And, as a final method of coercion, he would be forced to listen to a continuous loop of special-order speeches by Rep. Louie Gohmert (R-Tex.), blasted from loudspeakers 24 hours a day.

Within a few days, at most, Mnuchin would release Trump’s tax returns. Constitutional crisis averted.

Mnuchin’s confinement would benefit the American public in other ways, too:

It would prevent Mnuchin (previously the executive producer of “The Lego Batman Movie”) from doing any more harm as a negotiator for the United States in the just-collapsed trade talks with China.

It would also save taxpayers the expense of his lavish travel tastes, which had him flying to the solar eclipse with his wife on a military jet, inquiring about military aircraft for his European honeymoon and recently flying on Michael Milken’s jet.

And it would place behind bars a man who defended Trump’s response to Charlottesville, Trump’s foul language in public and Trump’s calls to defy the constitution.

Of course, in our democracy, Mnuchin would never be locked up for that. But a funny thing happens when you set off a constitutional crisis: The rules no longer apply.